Fix wide Unicode cell rendering

[ctate]

Fixes #54

[vercel]

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Project	Deployment	Actions	Updated (UTC)
wterm	Ready	Preview, Comment	May 16, 2026 8:56pm

[vercel]

Suggested change

	if (col === cursorCol) {
	appendStyledSpan("term-cursor", "", " ");
	}

When cursor is on a wide character's continuation cell (width=0), a redundant cursor-styled space span is emitted, breaking grid alignment.

[codevibesmatter]

👋 Stacked this on top of #81 locally + ran it against Claude Code's TUI in our identity-shell drawer on a production-ish staging deploy. The wide-char displacement that was producing visible artifacts in Claude's animated indicators (✦ Cooking for Xs, ✦ Herding…) — characters appearing 1 visual column right of where they belong, text fragments like "ightrrent branxh status" — is fixed by the combined branches.

Specifically the bug pattern that goes away:

• Animated wide glyphs (✦ U+2726, others) in Claude's spinner/progress UI no longer push subsequent narrow chars right by 1 cell per occurrence.
• The "Welcome back Ben!" intro panel's multi-column layout (left tips / center logo / right what's-new) lines up correctly because wide chars in panel headers don't shift cells anymore.
• Combined with fix(@wterm/dom): pixel-snap upper-block gradients to prevent sub-pixel misalignment #81's pixel-snapped gradient stops, Claude's ▔▔▔▔▔ horizontal rules render as a smooth line.

Heads-up on a pre-existing failure I hit running pnpm test on this branch: @wterm/react tests fail 14/14 with what looks like a useTerminal hook output-shape change that the test mocks weren't updated for. Doesn't touch the integration path (DOM + WASM both clean), but might block CI green.

Happy to ship the stacked-on-main rebase as a PR if it'd help unstick this one. Strong demand for it from a real-world Claude Code workload.